1. Field of the Invention
The present invention relates to a cable laying structure for an industrial robot and in particular to a cable laying structure for connection with an analogue camera, a digital camera or a force sensor, which is attached to a wrist of an industrial robot of a horizontal or vertical articulated type.
2. Description of Related Art
In recent years, it has been more and more common to equip a robot with a visual or force sensor in order to make the robot intelligent. In case that the robot is equipped with a visual or force sensor, it is required to attach camera cables for controlling a visual sensor or force-sensor cables for controlling a force sensor to the robot. For instance, JP 2001-145634A discloses a cable laying structure for an endoscope (camera) attached to a robot.
A camera utilized for a visual sensor is generally an analogue or digital camera. Analogue camera cables include a coaxial cable for transmitting a signal and a camera power cable, whereas digital camera cables include a signal cable for transmitting a digital picture signal and a camera power cable. On the other hand, utilized for the force-sensor cables are a signal cable for transmitting a detection signal of a strain gauge in a force sensor and a force-sensor power cable.
A cable structure usually employed is the one in which the whole cables are covered with a shield member and a sheath so that the picture signal of the camera and the detection signal of strain gauge of the force sensor are not affected by noise from without and so that noise does not leak outside. Therefore, the sheath and shield of the camera and force-sensor cables are indispensable. Consequently, as for a robot with a forearm portion having a wrist shaft movable in a wide range, the cables are managed while being supported by an external supporting member in consideration of the life of the cables as in the mode in which the cables are hung outside the forearm by a hanger.
FIGS. 1a and 1b illustrate the above arrangement. In the vicinity of the wrist of the robot 1, there is mounted an analogue camera, or digital camera, or force sensor C/S alongside of the hand 5. The cables CB connected to the camera or force sensor C/S are introduced into the inside of robot mechanism from the connection panel 3 with a connector, that is fixed to a base 2 of a robot 1, and drawn out of the robot mechanism in the immediate vicinity of the forearm 4. The cables CB that have been drawn out of the robot main body are hung by the hanger 9 mounted closely to the forearm 4 and pass the outside of the forearm 4 to reach the camera or force sensor C/S.
In a conventional cable laying structure, as described above, the camera cables that control the visual sensor (analogue or digital camera) mounted closely to the tip end of the robot wrist or the force-sensor cables that control the force sensor are embedded in the robot arm up to the immediate vicinity of the forearm. From the forearm portion to the tip end of the wrist, however, the cables are hung by the hanger or the like, that is attached on the outside of the robot arm, to be managed as far as the tip end of the robot wrist.
For this reason, when the robot system is actually utilized, the cables are liable to interfere with peripheral devices, which often becomes a problem in the field.